Wafer container with staggered wall structure

ABSTRACT

A wafer container comprising a base and a cover that nest together. The base includes a staggered wall structure composed of inner and outer walls. The staggered wall structure is arranged so that forces from side impacts are absorbed principally by outer wall segments. A rib on the cover restrains the outer wall segments from flexing beyond the inner wall diameter. Reference tabs on the base facilitate alignment of the base to the cover.

BACKGROUND OF THE INVENTION

Semiconductor wafers are fragile substrates that can easily becomescratched or damaged if not properly protected during transport. Eachsemiconductor wafer is patterned with numerous integrated circuits on asilicon substrate. Numerous containers have been developed to protectsemiconductor wafers from damage during shipping and handling.

Frequently, the top and bottom half of wafer containers are improperlycombined by an operator or become misaligned by forces that impact thecontainers during shipping. Such misalignment may contaminate, crack, orotherwise damage the valuable wafers stored within the containers.

Among the variety of horizontal wafer containers for semiconductorwafers, are containers having a dual wall structure. U.S. Pat. No.6,193,068 (Lewis) is one example. The double walls in Lewis weredesigned to protect wafers from forces that may contact the outer wallof the base. However, in Lewis the outer wall is directly behind theinner wall and is aligned in a similar angular sector. Inner walls insuch wafer containers are generally rigid and inadequately shockabsorbent. An external force may be substantial enough to flex the outerwall into the inner wall, which in turn would damage the wafers storedwithin the wafer container.

There remains a need for a wafer container that is less prone tobecoming separated and that is sufficiently robust to protectsemiconductor wafers from forces transmitted during shipping andhandling.

SUMMARY OF THE INVENTION

The present invention concerns a wafer container having a dual wallstructure on the base. The wall structure comprises multiple outer wallsand multiple inner walls. Each inner wall shares a minimal percentage ofa common angular sector with each adjacent outer wall.

The present invention also concerns an alignment system for facilitatingthe proper alignment of a cover with a base. The alignment systemincludes reference tabs that are received by the cover and a visualidentifier for guiding an operator in the proper alignment of the twohalves of the container.

Another embodiment of the invention concerns a locking mechanism forsecuring two halves of a wafer container together. The bottom halfcomprises a wall structure perpendicular to the base. The wall structurecomprises segmented inner and outer walls, each portion of the wallstructure has a distinctive arc length. The arc length of each innerwall does not completely overlap with the arc length of any outer wall.

Yet another embodiment of the invention concerns a cover for a wafercontainer that engages to a base. The cover includes one or morenotches, each having a ramp that easily receive latches from the base.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the container of the present inventionshowing wafers interposed between both halves of the container;

FIG. 2 illustrates reference tabs on the base in alignment with thecover.

FIG. 3A illustrates reference tabs in alignment with a cover.

FIG. 3B illustrates reference tabs in misalignment with a cover.

FIG. 3C illustrates a cover with alignment arrows to facilitate properorientation to a base.

FIG. 4A illustrates the height dimension of the hook portion of thelatch.

FIG. 4B illustrates the height dimension of the reference tabs of FIG.2.

FIG. 5 illustrates the container of FIG. 1 with the top cover beingsecured to the bottom half.

FIG. 6A is a side view of the closed container of FIG. 5.

FIG. 6B is an alternate side view of the closed container of FIG. 5.

FIG. 7 illustrates the location of angular sectors on the base of thepresent invention.

FIG. 8 is a top view of the base.

FIG. 9 is a perspective view of the base of the present invention.

FIG. 10 is a perspective view of the interior of the top cover.

FIG. 11 is an exploded view of the ramp in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

The container of the present invention stores semiconductor wafers, orsemiconductor film frames. FIG. 1 illustrates the two halves of thecontainer, a base 100 and its corresponding cover 200. A ribbed pattern30 on the floor 10 of deck 60 serves to reinforce the integrity of base100. The storage area of base 100 is defined by inner walls 80, floor10, and outer walls 90A, 90B, 92A, and 92B. Interposed between cover 200and base 100 are wafers 30, 32 and wafer separators 37-39.

Upon impact, outer wall segments 90A, 90B, 92A, and 92B will flex to theinner diameter 12 of inner wall segments 80. Outer wall segments 90A,90B, 92A, and 92B absorb the bulk of energy from side impact, therebytransferring a reduced amount of energy to the inner wall segments 80.Consequently, wafers 30 and 32 are sheltered from the brunt of forcefulimpact by the staggered wall structure of the invention.

FIG. 2 illustrates an alternative embodiment for the base 100 of wafercontainer 250. In this more preferred embodiment, a series of referencetabs are mounted on deck 60 of base 100. Reference tabs 20A, 20B, 22A,22B, 24A, 24B, 28A, and 28B are designed to help align base 100 withcover 200 in the following manner. Cover 200 has support brackets thatare designed to register with tabs 20, 22, 24, and 28. In particular,recess 70A of bracket 70 loosely fits over tab 20A, while recess 70Bloosely fits over tab 20B. Similarly, recess 78A fits over tab 28A (notshown), while recess 78B slips over tab 28B. Recesses 74A and 74B fitover tabs 24A and 24B respectively. Preferably, none of the recesses ofsupport brackets 70, 72, 74, 78 will snugly fit onto tabs 20, 22, 24,and 28. In the most preferred embodiment, each of the four supportbrackets will be identical and have the appearance of support bracket70. FIG. 3C illustrates cover 200 where the all of the support bracketshave an identical structure.

In FIG. 3A, a top view of base 100 is shown along with a skeletal viewof cover 100. A hatched outline is used to indicate cover 200 and howcover 200 is properly aligned to base 100. A latch 25 on each corner isalso shown in FIG. 3A. Adjacent to each latch is an opening 31 whichprovides latch 25 latitude for moving into a latched or unlatchedposition. Pairs of references tabs are located on each side of an uppersurface of base 100. For example, in FIG. 3A, tabs 24A and 24B arelocated on one side of base 100 between openings 31C and 31D, while tabs28A and 28B are located on an adjacent side of base 100 between openings31A and 31D. Similarly, tabs 22A and 22B are located on a different sideof base 100 between openings 31B and 31A. Tabs 20A and 20B are locatedon a fourth side of base 100. FIG. 3B illustrates cover 200 of FIG. 3Aafter it has been rotated 90°. In the position of FIG. 3B, cover 200 ismisaligned with its base 100. Cover 200 can not properly fit onto base100 because recess 70A and recess 78A do not register with reference tab20 A and reference tab 28A respectively. That is, the recesses ofsupport brackets 70 and 78 do not slide freely onto tabs 20A and 28A,thereby preventing cover 200 from being improperly positioned onto base100. FIG. 3B also illustrates orientations arrows 35 and 37. Orientationarrows 35, 37 provide a visual reference to assist an operator inproperly aligning cover 200 with base 100. In a preferred embodiment,cover 200 will also have a pair of orientation arrows as shown in FIG.3C that coincide with the arrows on base 100 when the two halves are inproper place relative to each other. Instead of an arrow, any other typeof visual mark may be used to assist an operator in identifying when thecover and the base are properly aligned.

The height dimension H1 of the latch hook is shown in FIG. 4A. Theheight dimension H2 of reference tab is shown in FIG. 4B. H2 should havea height that will prevent latch 25 from engaging to cover 200 if cover200 is not adequately pressed down onto base 100. In a preferredembodiment, H2>H1.

FIG. 5 illustrates a perspective view of the closed wafer container 250.Specifically, sidewall 75 and support brackets 70 and 74 of cover 200enclose the exterior of wall structure 80, 90, and 92 to form closedcontainer 250. The major surface 50 of cover 200 has a pattern thatprovides structural strength as well as stiffness to the top portion ofcontainer 250. In particular, it was found that adding a star shapedpattern 33 on cover 200 and concentric ribs 52, 54, resulted in a stiffand lightweight cover 200. The star-shaped pattern 33 is not limited tofour arms, but it can have more than four arms as shown in FIG. 3B. Base100 also has a latch 25 mounted on each corner of a deck 60. The twohalves of container 250 are secured when each latch 25 locks onto arespective notch 43 of cover 200 as shown in FIG. 5. Also visible inFIG. 5 is a lip 27 on the periphery of cover 200. This lip 27 enablesthe container 250 to be stacked on a second container identical to thefirst one.

To illustrate how the segmented wall structure of base 100 mates withits cover 200, a side view of container 250 is shown in FIGS. 6A and 6B.Wall segment 81 fits inside sidewall 75 of cover 200. Sidewall 75 hasslots 35, which allow a portion of outer walls 81 and 85 to be exposed.Similarly, outer wall 85 will fit inside sidewall 75 of cover 100 whenthe two halves 100, 200 are engaged. In addition, support brackets 70Aand 70B nest outside outer walls 83 and 87 of base 100, providing astable storage area for the wafers stored inside.

The various wall segments on base 100 occupy specific areas within acircumference on base 100. These areas are referred to herein as angularsectors. FIG. 7 illustrates one example of the angular sectors R1-R6that may exist within a circumference 50 located on base 100. R1, R3,and R5 represent angular sectors where an inner wall segment is to belocated, while R2, R4, and R6 represent areas where an outer wallsegment is to be located. The outermost boundary of each angular sectoris defined by an arc. Outermost arcs are indicated as 41B, 41D and 41F.The innermost arcs within circumference 50 are 41A, 41C, and 41E. Arc41A is shown as extending into angular sector 41F by an angle γ ofapproximately 2°. Arc 41C is shown as extending into both adjoiningsectors R4 and R2 by an angle θ₁ and θ₂, wherein θ₁ is approximately 3°and θ₂ is approximately 4°. Arc 41E extends from sector R5 by an angleα, which is approximately 5°. Although only six angular sectors areshown, the container can have eight or more angular sectors.

FIG. 8 is a top view of base 100, showing both the segmented walls 80,82, 84, 86, 90A, 90B, 92A, 92B and angular sectors R1-R8. The floor 10of deck 60 is shown without any ribbed pattern 30 to illustrate a moreclarified view of angular sectors R1-R8. However, it is understood thatthe ribbed pattern 30 is present in a preferred embodiment.Perpendicular, or nearly perpendicular, to base 100 are a series ofinner walls, 80, 82, 84 and 86. In addition, a series of outer walls90A, 90B, 92A, 92B are also perpendicular, or nearly perpendicular, tobase 100. Each of the walls shown has an arc with a specific arc length.For example, inner wall 86 has an arc 59 with an arc length 58.Similarly, outer wall 92A has an arc 53 with an arc length 56. Eachinner and outer wall occupies one of angular sectors R1-R8. Between 50and 99.5% of the inner wall arc is not located in the same angularsector as the arc of an adjacent outer wall. For example, over 90% ofthe inner wall arc 59 is located in R7, and occupies virtually none ofthe adjoining angular sectors R6 or R8. Outer wall 92A is located on arc53, and is located almost entirely within angular sector R4.Consequently, approximately 95% of outer wall 92A is not located inadjoining angular sector R3 or R5.

Since inner wall segments alternate with outer wall segments, the arc ofan inner wall may encroach into an adjoining angular sector. In apreferred embodiment of the invention, the arc length of each inner wallsegment encroaches approximately 0 to 50% of the arc length of anadjoining angular sector of an outer wall. In a more preferredembodiment of the invention, inner wall 82 occupies angular sector R3and shares between 0.1% to 25% of angular sector R4 with outer wall 92A;inner wall 82 also shares between 0.1% to 25% of angular sector R2 withouter wall 90A. Most preferably, inner wall 82 shares between 0.1% to10% of angular sector R4 with outer wall 92A and between 0.1% to 10% ofangular sector R2 with outer wall 90A. Similarly, inner wall 80, whichprincipally occupies angular sector R1, preferably shares between 0 to50% of angular sector R2 with outer wall 90A and between 0-50% ofangular sector R8 with outer wall 92B. More preferably, inner wall 80shares between 0.1% to 25% of angular sector R2 with outer wall 90A;inner wall 80 also shares between 0.1% to 25% of angular sector R8 withouter wall 92B. Most preferably, inner wall 80 shares between 0.1% to10% of angular sector R2 with outer wall 90A and between 0.1% to 10% ofangular sector R8 with outer wall 92B.

The invention is not limited to a container that has only the eightangular sectors R1-R8 shown in FIG. 8. The invention will work with abase having fewer than eight angular sectors, as well as a base withmore than eight angular sectors. The number of sectors will equal thetotal number of inner and outer wall segments. The arc of each wallsegment defines an outermost boundary of each angular sector. Althougheach wall (80, 82, 84, 86, 90A, 90B, 92A, and 92B) in FIG. 8 separatelyoccupies less than 90° of the base circumference (i.e., each wallpreferably has an arc length less than (Π/2 radius)), it is notnecessary that this always be the case for the invention to work. Inother words, each wall can occupy a greater angular portion of thecircumference. Moreover, each inner wall (80, 82, 84, 86) need not havethe same arc length as every other inner wall. Similarly, it is notessential for each outer wall (90A, 90B, 92A, and 92B) to have the samearc length as every other outer wall on base 100. Also shown in FIG. 8is a latch 25 mounted on each corner of base 100. On the rear of latch25 is a rib 23. Rib 23 is an optional feature for strengthening latch25. Although four latches are shown in FIG. 5, the invention will worksatisfactorily if only two latches are present.

FIG. 9 illustrates the bottom half of the wafer container 250, alsoreferred to herein as base 100. The wall structure of base 100 includessegmented inner walls and segmented outer walls. A continuous wallstructure is disadvantageously very stiff, even in the presence of oneor two lateral openings. By providing a segmented wall structure, innerwalls 80, 82, 84 and 86 are more flexible and shock absorbent. As aresult, walls 80, 82, 84 and 86 sufficiently cushion wafers withincontainer 250 if the container is dropped or otherwise subjected toforceful impact.

Outer walls 90A, 90B, 92A and 92B are staggered relative to inner walls80, 82, 84 and 86 as shown in FIG. 9. This staggered double wallstructure provides maximum protection from shock to wafers stored incontainer 250. In addition, outer walls 90A, 90B, 92A, and 92B have agreater flexible tolerance when their angular sector has minimum overlapwith the angular sector of an adjacent inner wall. Outer walls 92A and92B each have a slot 15. Preferably the lower portion of slot 15 doesnot extend to the same level as deck 60. Slot 15 enables an operator armto more easily access wafers stored within base 100.

The deck 60 of FIG. 9 also includes latches 25 for securing base 100 tocover 200. Each latch 25 has a proximal end that is mounted on a cornerregion 60 of base 100. The distal end of each latch 25 terminates in ahook 25A that grasps onto cover 200.

A detailed view of the cover 200 is shown in FIG. 10. On the interiorsurface 44 of cover 200 are a series of concentric ribs 51, 52, 54.Outermost rib 54 may contact a portion of the wall structure on base 100if wafer container 250 is subjected to external forces. During shippingor handling, when closed container 250 encounters a forceful sideimpact, outer wall segments 90A, 90B, 92A and 92B absorb the bulk of theimpact by flexing inward toward the inner diameter 12 of inner wallsegments 80. The outer wall segments 90A, 90B, 92A and 92B arerestrained from flexing beyond diameter 12 by rib 58 on the interior ofcover 200.

In addition to ribs, cover 200 contains a sidewall 75 that extendsperpendicularly from surface 44. In a preferred embodiment, two slots 35are present in sidewall 75. Slots 35 are each surrounded by supportbracket 71 or 73. Support brackets 70A and 70B are also attached tosidewall 75 on cover 200. Support brackets 70, 71 and 73 serve to orientcover 200 into a proper position on base 100. Bracket 73 has two fins77A and 77B connected together by a narrow tie 74 so as to form recesses72A and 72B. In addition, located within support bracket 71 are recesses74A and 74B. The four corner regions 60 of cover 200 each have a notch43 for receiving a respective latch 25. To enhance the security of cover200 from becoming disengaged from base 100, notch 43 is provided with aramp 85.

FIG. 11 illustrates an exploded view of the locking mechanism of theinvention that secures cover 200 to base 100. A notch 43 is shown havinga rectangular shape. The longer edge of notch 43 has a ramp 85. Suitableangles for ramp 85 range from 5°-30° from the planar surface of cover200. To secure cover 200 to base 100, notches 43 are aligned above theircorresponding latches so that hook 25A can enter notch 43. Latch hooks25A then slip downward over the positive slope of a ramp 85, i.e.positive relative to the top surface 50 of cover 200. Once latch 25locks into place, cover 200 is securely engaged to base 100. Todisengage cover 200 from base 100, an operator pushes back on hook 25Auntil it clears notch 43, and then the cover 200 is lifted away frombase 100. Although notch 43 is shown to be rectangular, it can also haveother shapes, such as a “T” or an ellipsoidal shape.

The examples described herein of the various segmented walls are solelyrepresentative of the present invention. It is understood that variousmodifications and substitutions may be made to the foregoing examplesand methods of operation of the wafer container without departing fromeither the spirit or scope of the invention. In some instances certainfeatures of the invention will be employed without other featuresdepending on the particular situation encountered by the ordinary personskilled in the art. It is therefore the intent that the scope of theinvention is to be defined by the appended claims.

1. A wafer container comprising: a base, wherein a circular region ofthe base has a circumference that includes a plurality of angularsectors; a first wall attached to the base along a lower edge of saidfirst wall, said first wall having a first outer arc that defines afirst angular sector: a second wall attached to the base along a loweredge of said second wall, said second wall having a first inner arc,said first inner arc defining a second angular sector, wherein the firstwall and the second wall share between 0 to 50% of a common angularsector; a third wall along a second outer arc, said second outer arcdefining a third angular sector, and a fourth wall along a second innerarc, said second inner arc defining a fourth angular sector, wherein thethird wall and the fourth wall are each attached to the base along alower edge of their respective walls, and wherein the third and fourthwalls share between 0 to 50% of a common angular sector; a wallstructure formed by the first, second, third and fourth walls; and acover that engages the base to form a closed container.
 2. The wafercontainer of claim 1, further comprising a series of additional wallstotaling a sum of k walls, wherein k is an integer greater than 4, andwherein the kth wall has an arc that shares between 0 to 50% of a commonangular sector with said first wall and wherein each inner arcalternates with an outer arc along said circumference.
 3. The wafercontainer of claim 1, wherein the walls of the wall structure sharebetween 0.1% to 25% of a common angular sector.
 4. The wafer containerof claim 1, wherein the walls of the wall structure share between 0.1%to 10% of a common angular sector.
 5. The wafer container of claim 1,wherein said cover includes a ramp adjacent to each notch, said ramphaving a slope for guiding a latch on the base into engagement with itsrespective notch.
 6. The wafer container of claim 1, wherein said basehas four corners and a latch is mounted on at least two of said corners.7. A wafer container comprising: a base, wherein a circular region ofthe base has a circumference that includes a plurality of angularsectors; a wall structure comprising segmented inner walls and segmentedouter walls, wherein each inner wall is separated by a space from eachouter wall, and said wall structure is perpendicular to the base, eachinner wall being located on a respective first arc on the base and eachouter wall being located on a respective second arc on the base, whereinbetween 50 and 99.5% of the arc length of said first arc is not locatedin the same angular sectors as the arc length of said second arc; and acover that engages to the base to form a closed container.
 8. The wafercontainer of claim 7, wherein at least 90% of the arc length of saidfirst arc is not located in the same angular sector as the arc length ofsaid second arc.
 9. The wafer container of claim 7, wherein eachsegmented inner wall occupies less than 90° of said circumference. 10.The wafer container of claim 7, wherein said segmented inner wallsalternate with said segmented outer walls.
 11. The wafer container ofclaim 7, wherein said cover contains a notch having a ramp for receivingthe base.
 12. The container of claim 11, further comprising a pair oflatches connected to the base, wherein the latches secure the base tothe cover when each latch locks onto a respective ramp on the cover. 13.A wafer container comprising: a top cover having a major surface, and afirst wall structure extending from said major surface; a plurality ofsupport brackets projecting from said wall structure; a notch on eachcorner of said cover; a base having a plurality of latches that engagewith a respective notch on the top cover; wherein each notch has a firstand a second edge, the second edge being longer than the first edge,wherein the second edge has a ramp for receiving a corresponding latchfrom the base.
 14. The wafer container of claim 13, further comprising agap in the wall structure, wherein one of said support bracketssurrounds one side of said gap.
 15. The wafer container of claim 13,further comprising a second wall structure that is perpendicular to thebase, said base having a circular region that has a circumference thatincludes a multiple angular sectors, wherein said wall structureincludes inner wall segments that alternate with outer wall fragments,and wherein each inner wall segments shares between 0 to 10% of a commonangular sector with the next alternating outer wall segment.
 16. Thewafer container of claim 13, further comprising a plurality ofsemiconductor wafers stored therein.
 17. A wafer container comprising: abase having an upper surface upon which is located a circumference; awall structure extending from said base, said wall structure havinginner wall segments that alternate with outer wall segments, whereineach inner wall segment is attached to the base at a lower edge of theinner wall, and each outer wall segment is attached to the base at alower edge of the outer wall; a pair of reference tabs located on eachside of said upper surface; and a cover that aligns with said referencetabs to from a locked wafer container.
 18. The wafer container of claim17, wherein said cover includes support brackets attached to a firstsurface of said cover, and wherein each support bracket has a pair ofrecesses that interlock with a corresponding pair of reference tabs. 19.The wafer container of claim 17, further comprising a latch in at leasttwo corners of said base.
 20. The wafer container of claim 19, whereinthe cover has a notch that receives a latch from said base, each notchhaving a first and a second edge, the second edge being longer than thefirst edge, and wherein the second edge has a ramp for receiving acorresponding latch from the base.
 21. The wafer container of claim 17,further comprising a plurality of semiconductor wafers stored therein.22. The wafer container of claim 17, further comprising a visual mark onthe upper surface of said base and on the cover to facilitate alignmentof the base with the cover.